Japanese Patent Laying-Open No. 4-295202 has disclosed an electric motor drive and a power processing device that can transmit and receive an electric power between an alternating-current (AC) power supply outside a vehicle and a direct-current (DC) power supply on the vehicle. This device includes a DC power supply, two inverters undergoing pulse width modulation (which may also be referred to as “PWM” hereinafter), two induction motors, a control unit, an input/output port and an EMI filter. Each induction motor includes a Y-connected winding, and the input/output port is electrically connected to a neutral point of each winding.
When this device is in a recharge mode, a DC power supply can be charged with a DC power produced by converting an AC power that is applied to the neutral point of each winding from a single-phase power supply connected to the input/output port. Also, a regulated AC of a sinusoidal wave can be generated between neutral points of the windings and can be provided to an outer device connected to the input/output port.
The EMI filter is arranged between the neutral point of each winding and the input/output port, and reduces common mode noises of high frequencies appearing on the input/output port.
However, Japanese Patent Laying-Open No. 4-295202 employs the EMI filter for reducing the common mode noises that appear due to high-frequency switching of the inverters so that the device has large sizes.